In the past, tools have been fabricated to achieve various hardness, lubricity and wear characteristics by controlling certain parameters. For example, tools for working and shaping unhardened steels may be fabricated from steel containing enough carbon to form very hard martensite. In more complicated compositions, varying the carbon content and alloy content makes possible non-deforming steels, shock-resistant steels, hot-work steels, or high-speed steels. In some of these steels, alloying elements such as titanium, vanadium, molybdenum, tungsten and chromium are used. These are elements which have a great affinity for carbon and form hard, wear-resistant metallic carbides. However, in many cases, it is desirable to provide a tool having a coating on the surface thereof to improve the hardness and/or lubricity of the tool. This is especially the case where it is desired to lengthen the tool life, or where it is necessary to shape and work hardened steel. However, many refractory hard tool coatings, for example refractory oxides, carbides, nitrides, and borides have a very low lubricity. Moreover, some refractory oxides, e.g., alumina, have a highly irregular topography. The combination of irregular topography and low lubricity militates against the use of certain refractory compounds as tool coatings.
This is also the case where it is desired to provide a hard layer atop an underlying soft, elastic, or deformable layer, where the hard layer protects the substrate from degradation.
A need exists for a wear resistant coating that retains the hardness of refractory compounds while avoiding the low lubricity and irregular topography of many refractory compounds. A need also exists for a wear resistant coating that retains the desirable properties of such refractory coatings as alumina and has improved adhesion properties and resistance to fracture. Similarly, a need exists for a external wear resistant coating atop an underlying soft, deformable, or elastic layer, as a stainless steel or chromium layer.